The word 'thereby' is a compound formed from the Old English adverbs 'there' and 'by'. Its construction follows a common Germanic pattern for creating adverbial phrases of means or consequence. Literally, it meant "by that (place/thing)" or "near that," with 'there' serving as a demonstrative pronoun referring to something previously mentioned. Over time, the spatial sense weakened, and the logical, consequential meaning became dominant. It evolved from indicating a physical or instrumental connection ("by means of that") to expressing a figurative or legal result ("as a consequence of that action").

Structure: there + by - there: From Old English þǣr, þār (in or at that place). A demonstrative adverb of place. - by: From Old English bī (near, at, during, according to). A preposition/adverb indicating proximity, agency, or means.